This invention concerns automotive car wash conveyors, and more particularly pusher roller assemblies used in three track type conveyors.
Automatic car washes use conveyors for pulling each car along a track extending through an array of car washing equipment disposed along the conveyor.
One design which has been widely adopted uses a series of roller assemblies attached to an endless recirculated chain extending around a three track structure extending the length of the conveyor.
The roller assemblies move forwardly down an intermediate track and return on a lower track, the chain circulating along both tracks. When a car advances onto the upper track and a pusher roller assembly is needed, a forked ramp is raised from the intermediate track to intercept and guide an upper pusher roller set of the roller assembly onto an upper slotted track along which the car tires roll. An elongated roller bar has the pusher roller set mounted thereon and extends down through the slot to the chain. A set of idler rollers are mounted to the other end of the dog to provide rolling support for the chain and roller assemblies on the intermediate and lower return tracks.
The pusher roller set rolls along the upper track and also engages the car tire. Two pusher roller pairs are provided, one for engaging the car tire and the other for engaging the upper track.
In early versions of this design, the tire engaging and track engaging rollers were provided by stepped diameters of a common roller as seen in U.S. Pat. No. Re 30,026 reissued on Jun. 12, 1979 for a "Vehicle Conveyor".
Due to problems with wide tires, the pusher roller sets are now typically provided with separately mounted pairs of rollers, each roller of the pairs cantilevered out from one side of the dog, so that six separate rollers are included in each roller assembly.
An example of this arrangement is shown in U.S. Pat. No. 4,873,929 issued on Oct. 17, 1989 for a "Pusher Unit" U.S. Pat. No. 4,314,496 issued on Feb. 22, 1983 for a "Vehicle Conveyor", and U.S. Pat. No. 4,930,424 issued on Jun. 5, 1990 for a "Conveyor Chain Guide".
An improved design for the separately mounted pusher rollers is described in U.S. Pat. No. 4,864,936 issued on Sep. 12, 1989 to the assignee of the present application, which design has proved to have provided a long wear life roller assembly.
In these prior conveyors, the rollers are constructed of a durable molded plastic such as urethane, and are mounted on shafts cantilevered out from each side of the roller bar. The ends of the rollers are hollowed out to enclose the heads of bolts used to hold the rollers in place. This arrangement has created a tendency for the rollers to "grow" in length due to the pressure of the engagement on the unconfined outer end of the roller. The rollers may jam between the track sides as a result of their increased length.
The upper pusher rollers are of smaller diameter than the lower idler rollers, and one roller pair in the pusher set runs along all three tracks.
Due to the small diameter of those rollers, early wearout of the pusher rollers has been a problem, which is a major maintenance burden, as replacement often requires disassembly of the chain and roller assemblies. One set of rollers is used to engage the forked ramp, and if excessive wear of that roller set has occurred, proper engagement with the ramp may not be possible, rendering that roller assembly inoperative. This is a particular problem where "coning" wear of the roller creates a tendency for the rollers to track to one side in ascending the fork ramp. As the rollers are typically not replaced until complete wearout has occurred, further maintenance often must be done as a result of roller wearout.
The construction of the prior art roller assemblies has also led to high manufacturing costs, and also misalignments of the rollers in each pair is common.
Applicant has heretofore also sold roller assemblies using three pairs of pusher rollers in attempt to reduce wear, but this design involved two sets of rollers rolling on the upper track when not engaged such that no real wear reduction resulted.
Accordingly, it is an object of the present invention to provide a pusher roller assembly of the type described in which the frequency of roller replacement required as a result of roller wear is reduced.
It is another object of the present invention is to provide such a pusher roller assembly which may be manufactured at low cost and insures good alignment of the rollers in each pair.